The above descriptions and definitions are illustrated by a series of plates, containing above 500 etchings of nearly as many proposed or established genera, arranged in Lamarckian order, so as to show at a glance all the generic forms of each family. And, although from their number, they could not be very highly finished, it is hoped that they will be found characteristic. The compiler cannot replace his pen without acknowledging, with filial gratitude, the kind assistance of one who has sacrificed much of his time in bringing his knowledge and experience to bear upon the correctness and utility of this humble attempt to remove some of the difficulties to which the commencement of this, as well as of every other study, is exposed. PREFACE TO THE SECOND EDITION The favourable reception and rapid sale of the first edition of the Conchological Manual having rendered a second necessary, the Author takes this opportunity of explaining the nature of the alterations which have been made. In doing this, he has to thank his friends for their suggestions, which, together with his own increased knowledge and experience, enable him to present a more complete and satisfactory work to the scientific public. For the further convenience of those who are studying the rudiments of the science, an entirely new Introduction is given, in which, commencing with the structure and gradual developement of the shell, the author has endeavoured to explain the general principles of Conchology in systematical order. This Introduction is illustrated by 100 wood-cuts, which will be found greatly to assist the Student. The definitions have been rendered more full and complete than before, and the Author has profited by some manuscript notes communicated by a scientific friend, to whom he desires to present his humble acknowledgments. Upwards of four hundred explanations have been given of words which did not appear in the former edition, three-fourths of which are of generic and subgeneric names. A large number of notes, referring to the geographical distribution of the genera, have been added from the pen of Mr. G. B. Sowerby, Senior. The plates have been carefully improved; and three, containing upwards of eighty figures, have been added. On the whole, it will be found that the amount of matter has been nearly doubled; all the defects, as far as they have been discovered, have been removed, and every means used of making the present edition as useful as possible. * * * * * NAMES OF AUTHORS ABBREVIATED. _Adans._ Adanson. Author of "Voyages du Senegal." _Bl._ Blainville. Author of "Manuel de Malacologie et de Conchyliologie," &c. _Brod._ W. J. Broderip, Esq. Author of various descriptions of Shells in the Zoological Journal, &c. _Brongn._ Brongniart. Author of "Memoire sur les terrains du Vicentin, d'Italie, de France, et d'Allemagne," &c.